Method and equipment for mounting part

ABSTRACT

The present invention is to provide a method and an apparatus for mounting components having a feature of detecting with high accuracy component pick up failure by the nozzle at component pick up stage, and/or component carrying back by the nozzle at component mounting stage. Achieved vacuum pressure is initialized to zero after completion of component pick up by the nozzle  25 , and vacuum pressure decrease of the nozzle  25  is detected from the initialized zero point. If the detected value is bigger than the predetermined threshold, it may be judged that at least one of the nozzles failed to pick up a component. The failed nozzle may be identified by using a component recognition device  37 . Blowing air blow volume flowing through the nozzle  25  is measured upon completion of component mounting. If the blowing air flow is smaller that the predetermined threshold, it is judged that the nozzle  25  carries back a component  30 . Two thresholds may be used, and it may be judged that the component has been properly mounted if the measurement value is bigger than both thresholds, filter  22  is clogged if the measurement value is in between the two thresholds, and the nozzle  25  carries back the component if the measurement value is smaller than both thresholds.

TECHNICAL FIELD

Present invention relates to a method and apparatus for mountingcomponents by picking up components, such as electronic components fromcomponent supply, and mounting the same onto respective predeterminedpositions of a circuit substrate. More specifically, the presentinvention relates to a method and apparatus for mounting components,including procedures for detecting whether or not a nozzle for pickingup a component fails to pick up a component at component pick up stage,and/or detecting whether or not a nozzle fails to mount a component atcomponent mounting stage and carries back the component.

BACKGROUND ART

Component mounting apparatus having nozzles for picking up components bymeans of sucking effect generated by vacuum pressure generallycomprises: a component supply for supplying components continuously to acomponent mounting apparatus; a mounting head holding one or morenozzles for picking up components from the component supply and mountingthe same onto a circuit substrate; a transporting device fortransporting the mounting head to and from the mounting position; acomponent recognition device for recognizing and determining conditionof the component held by the nozzle; and a substrate holder fortransporting a circuit substrate into the component mounting apparatusand placing the circuit substrate at its position.

The component mounting apparatus as structured above operates asfollows. First, a plurality of nozzles held by the mounting head pick upcomponents supplied at the component supply continuously. Then, themounting head is moved by the transporting device over the componentrecognition device, during which time a recognition camera of therecognition device images condition of the component held by the nozzle.The mounting head is moved further toward the position where the circuitsubstrate is firmly held at its position by the substrate holder. Themounting head stops at the position facing a predetermined mountingposition of the circuit substrate so that the nozzles may descendagainst the circuit substrate and mount the components onto the circuitsubstrate. All of the above operations performed by the componentmounting apparatus are controlled by a controller mounted inside thecomponent mounting apparatus.

Sucking components with a plurality of nozzles at pick up stage, as wellas separating the components from the associated nozzles at mountingstage are regulated by switching operation of the nozzle. The nozzle isconnected to either vacuum supply source or pressurized air supplysource by a switching device using electromagnetic valve or the like.More specifically, when picking up a component, the switching deviceregulates the nozzle to be connected to vacuum supply so that the nozzlemay pick up the component by means of sucking effect of vacuum pressure.When mounting a component, the switching device change the connection ofthe nozzle from vacuum supply source to pressurized air supply source sothat the nozzle may separate the component and mount the same onto thecircuit substrate by means of air blowing effect.

In recent years, many types of electronic components have beendeveloped, and needs for multi-functional component mounting apparatuscapable of mounting a variety types of component are arising. Majorissue for such a multi-functional component mounting apparatus is notonly to perform high speed and flexible mounting, but also to have acapability of preventing occurrence of defective products, such ascircuit substrates with missing components, and to have a capability ofimproving overall mounting quality.

In order to prevent occurrence of defective circuit substrates, thenozzle needs to pick up the component from the component supply withoutfailure, and needs to mount the component properly onto thepredetermined position of the circuit substrate. Toward this end, anozzle without holding a component for some reasons, such as lack ofcomponent supply or failure of pick up operation, needs to be detectedby using the component recognition device. When such a nozzle withoutholding a component is detected, component mounting operation by such anozzle is to be skipped, and the nozzle is arranged to repeat the sameoperations from component pick up to component mounting so as to preventoccurrence of defective substrate with missing components.

The nozzle is also checked after completion of mounting operation byusing the component recognition device or other sensors with theintension of finding out whether or not the nozzle carries back thepicked up component for some reasons, such as failure of componentseparation at component mounting stage. When it is detected that thenozzle is carrying back the component, the nozzle or any other nozzlesis to be arranged to repeat the same operation from component pick up tocomponent mounting so as to prevent occurrence of defective substrates.

As components to be mounted on a circuit substrate are becoming smaller,and the number of components to be mounted on a single circuit substrateis increasing in these days, the size of nozzle tends to be smaller formatching the small sized component, and for avoiding interference withneighboring components having been mounted on the same circuitsubstrate. In this connection, an area of a nozzle opening through whichsucking or blowing air passage is narrowed, thereby amount of vacuum airor pressurized air passing through the nozzle is limited. Accordingly,rate of occurrence of failure during sucking and mounting operationstends to increase recently. From such perspective, it becomes veryimportant to detect and find out whether or not the nozzle fails to pickup a component and/or whether or not the nozzle carries back a componentin order to prevent occurrence of defective substrates.

DISCLOSURE OF INVENTION Problems to be Solved by the Present Invention

Even if the component recognition device could detect that the nozzlehas successfully picked up the component, there is a possibility thatthe nozzle might drop the component after such detection by therecognition device has completed. In such a case, there are no otherdetecting devices disposed after the position of the componentrecognition device, and the nozzle without having a component wouldperform mounting operation, whereby the circuit substrate would be adefective product due to missing component. In a similar manner, even ifthe component recognition device could detect that the nozzle no longerhas a picked up component after component mounting operation, hence thenozzle is not carrying back the component, there is a possibility thatthe nozzle has failed to separate the component during mountingoperation, but the nozzle later has dropped the component beforereaching to position of the component recognition device. This case toocauses occurrence of defective substrate, since component missing mightnot be detected at any timing.

To cope with such situations, it is known in prior art a variety oftechniques for minimizing traveling distance and traveling time of themounting head between mounting position and detecting position, andtechniques for detecting the nozzle as early as possible aftercompletion of component mounting operation. In this specification,detecting component loss during and after component pick up operation ishereinafter referred to as “component loss detection”, while detectingcomponent carried back by the nozzle is hereinafter referred to as“mounting failure detection”, and these two phenomena are distinguishedfrom each other.

First, with regard to component loss detection, it is known in prior artto monitor vacuum pressure in the nozzle by means of a vacuum sensor,and to found out component loss when vacuum pressure decreases lowerthan a certain threshold (i.e., when vacuum pressure becomes closer tonormal atmosphere than the threshold.). FIG. 18 shows principle of suchdetection. Referring to FIG. 18, vertical line represents vacuumpressure (stronger vacuum effect at higher level), and horizontal linerepresents time elapsing. Normally, at point A where a component isbeing held by a nozzle, higher vacuum pressure P1 is maintained since anozzle opening is closed by the component. When the component drops fromthe nozzle, the vacuum pressure becomes lower because the nozzle openingis cleared hence atmospheric air may flow into the nozzle. Assuming thata component drops at point B, vacuum pressure becomes lower than thepredetermined threshold P0 as time goes by, which makes it possible tojudge that the component is lost when the vacuum pressure reaches to thethreshold P0. Pressure level P2 is saturated pressure after thecomponent is lost.

According to the above mentioned measure, however, it may be effectivewhen the individual nozzle is connected to a respective vacuumgenerating source. If a system has a plurality of nozzles which performcomponent picking up operation by using a common vacuum generator, itbecomes difficult to make accurate judgment by the above system sincevacuum level to be achieved after completion of component pick upoperation may vary in wide range depending upon a variety of suckingconditions. Such phenomenon of vacuum pressure variation comes from thefact that when one of the nozzles failed to pick up a component, airleakage occurs at that nozzle, which causes negative impact on vacuumpressure at all other nozzles. For example, in case a nozzle having abig opening drops a component, or in case a plurality of nozzles dropthe associated components, influence of vacuum leakage is so big thatsucking power at other nozzles may be deteriorated even when sufficientvacuum pressure is supplied. In such a case where variance of vacuumpressure due to air leakage is big, it may be not possible to make anaccurate judgment that a component is lost only if vacuum pressurebecomes lower than the predetermined threshold P0.

One possible solution for the above problem in prior art is to employ aplurality of vacuum supply sources which may be connected to a pluralityof nozzles on one by one basis. In such a case, however, other problemsbecome evident in that sucking pressure becomes low, and timing responsewhen supplying vacuum pressure is deteriorated. As a plurality of vacuumsupply sources are disposed, weight of the mounting head increases,which gives negative impact on capability of high speed mountingoperation. In addition, having a plurality of vacuum supply sourceinevitably increases cost.

On the other hand, with regard to detecting mounting failure aftercomponent mounting operation, a method is known in prior art in which aflow meter as show in FIG. 19 is used. Referring to FIG. 19, a mountinghead 23 (i.e., index, in the shown example in FIG. 19) holds a pluralityof nozzles 25 on its circumference in a circular manner for rotatingintermittently. During such intermittent rotation of the mounting head23, each nozzle 25 sucks a component 30 and pick it up from componentsupply 31 at component pick up station located in a distant side in Ydirection of the drawing, and mount the component 30 onto a circuitsubstrate 5 at component mounting station M located at forehand side inY direction. A circuit substrate 5 is firmly held at its position bysubstrate holder 15.

According to the above method, a flow detecting station N is formed at acertain position after the component mounting station M, and air flowvolume blowing out of the nozzle 25 is detected by using a flow meter26. When a nozzle 25 arrives at the air flow detecting station N, thenozzle 25 descends toward a circular vessel surrounded by a ring typeseal, and blows air into the vessel in a sealed condition. The air flowvolume blown from the nozzle 25 is measured by flow meter 26 which isconnected to the circular vessel. If the nozzle 25 has failed to mount acomponent and is still holding it (carrying back), the air flow volumeis reduced due to blockage by the carrying component 30. The controller41 compares the measured air flow volume with a preliminarily inputtedthreshold, and make a judgment whether the component 30 is still carriedby the nozzle 25 or not. The result of the detection is shown on thescreen 28.

According to a method described above, certain improvement may beachieved, as component carrying back may be detected after componentmounting operation. Nevertheless, there still exists a drawback in theabove method in that the nozzle 25, which has completed mountingoperation, still needs to move for a certain length of distance in acertain length of time toward the flow volume detecting station N wherethe flow meter 26 is disposed. Therefore, there is a risk that thecomponent 30 may drop from the nozzle and be lost during the time ofsuch movement. It was not possible to measure air flow volume of thenozzle 25 at the component mounting station M with the intention ofavoiding the above risk, because there is no enough space for disposingthe flow meter 26. In the prior art, measurement result of such air flowusing the flow meter is utilized only for detecting mounting failure.

Accordingly, the purpose of the present invention is to provide a methodand apparatus for mounting components which may improve quality ofcomponent mounting operation by detecting phenomena during a componentmounting operation, which phenomena include a failure of picking up acomponent to be mounted, dropping of a component from the nozzle whichcomponent has been once picked up by the nozzle, and/or a failure toseparate a component for mounting and carrying back the component by thenozzle, all of which detection may be performed before or immediatelyafter the component mounting operation so as to avoiding anymisjudgment.

Means for Solving the Problems

The present invention solves the above described problems by thefollowing means. As for detecting component loss prior to componentmounting operation, achieved vacuum pressure at the time of completionof component mounting is initialized to zero, and vacuum pressuredecrease from the initialized zero point is detected and compared with apredetermined threshold. As for detecting mounting failure aftercompletion of component mounting operation, blowing air flow volume orair pressure used for separating a component from the nozzle is measuredand compared with a predetermined threshold. Through these procedures,component loss and/or component mounting failure may be reliablydetected, thereby the problems described above may effectively besolved. More specifically, the present invention includes the followingaspects.

One aspect of the present invention relates to a method of componentmounting for picking up components and mounting the same onto respectivepredetermined mounting positions of a circuit substrate by means of aplurality of nozzles connected to a single vacuum generating source, inwhich the method includes procedures for preventing occurrence ofdefective circuit substrates due to missing component, the procedurescomprise steps of: initializing achieved vacuum pressure of a nozzleafter completion of component pick up operation to zero; detectingvacuum pressure decrease of the nozzle from the initialized zero value;and if the detected vacuum pressure decrease exceeds predetermined firstthreshold, making a judgment that the nozzle has failed to pick up acomponent, and skipping component mounting operation by that particularnozzle.

According to the above method, component loss due to component drop fromthe nozzle after having been picked up by the nozzle may reliably bedetected without being affected by variance of the achieved vacuumpressure level after completion of component pick up operation, becausethe achieved vacuum pressure is initialized to zero. By initialing theachieved vacuum pressure after component pick up to zero, and pressurechange (vacuum pressure decrease) is detected from the initialized zeropoint, component loss due to drop may be reliably detected by providingonly one threshold, without being affected by achieved vacuum pressurevariance.

Furthermore, when component loss is detected by pressure changedetection, the particular nozzle without holding a component may bearranged to skip subsequent component mounting operation, thereby itbecomes possible to prevent occurrence of defective circuit substratedue to missing component. When component loss is detected, the nozzlewhich has lost the component may be identified through recognitionprocedures, and the nozzles other than such identified nozzle may beallowed to perform component mounting operations. Accordingly, componentheld by these other nozzles may effectively be utilized for mountingoperations, thereby waist of components may be avoided.

Another aspect of the present invention relates to a method comprisingsteps of: before initializing the achieved vacuum pressure of a nozzleto zero as described above, detecting absolute value of the vacuumpressure achieved by the nozzle after completion of component pick upoperation, and if the detected achieved vacuum pressure is lower thanpredetermined second threshold, shutting a vacuum air passage of thatparticular nozzle.

According to the above aspect of the present invention, absolute valueof the achieved vacuum pressure is detected, and it is judged that atleast one of the nozzles failed to pick up a component, and vacuum isleaking from that nozzle, if the measured value is smaller that thepredetermined second threshold. After identifying the nozzle that hasfailed to pick up a component, vacuum air passage of that failed nozzleis shut. By such procedures, vacuum air leakage may be prevented, andvacuum pressure connected to vacuum line is recovered, hence creatingstable sucking condition of nozzles other than the failed nozzle maybecome possible. It is also possible to generate an alarm signal upondetecting that the achieved vacuum pressure is smaller than the secondthreshold, since there is a possibility that other nozzles may droppicked up components due to the lower sucking power.

The nozzle that has failed to pick up a component may be identified byimage date by scanning each nozzle with recognition camera. Through suchprocedures, vacuum air leakage from the failed nozzle may be preventedby identifying the failed nozzle by using a simple system including arecognition camera, since the nozzle without having a component may beidentified by image data obtained by scanning of the camera.

It is also possible to image the nozzles one more time for detectingwhether or not any of the nozzles have lost a component afteridentifying the failed nozzle based on the image data and shut thevacuum air passage of the identified nozzle. According to thisprocedure, it becomes possible to more accurately detect nozzles withoutholding components, by imaging the nozzles by the recognition cameraagain after the vacuum air passage of the identified nozzle is shut.

All the nozzles, except the nozzles which are detected that componentsare not being held and the nozzles whose vacuum air passages are shut,may be allowed to perform component mounting operation. Therefore,components held by those nozzles need not be discarded, but rather beeffectively utilized through component mounting operation.

Another aspect of the present invention relates to a component mountingapparatus comprising: a vacuum generating source; a plurality of nozzlesconnected to said vacuum generating source, each of which nozzles has acontrol valve capable of shutting a vacuum air passage; a mounting headbeing supported in a movable manner and holding said plurality ofnozzles; a component recognition device positioned to face with themounting head for recognizing components held by the nozzles; and acontroller for controlling operations of the component mountingapparatus in accordance with a method according to any one of the abovedescribed method.

According to the above component mounting apparatus, the nozzle may beregulated either in open condition or in closed condition. When thenozzle is in open condition, the nozzle may suck and hold a component.By moving the mounting head over a component recognition device aftercomponent pick up operation, it becomes possible to identify whichnozzle holds a component and which nozzle does not. The controller thencontrols component mounting operation according to either one of themethod described above. The mounting operation may not be affected byvariance of achieved vacuum pressure after completion of component pickup, and may prevent occurrence of defective circuit substrate sincecomponent loss from the nozzle may be reliably detected.

Yet another aspect of the present invention relates to a method ofcomponent mounting for picking up a component by means of vacuum suckingeffect of a nozzle, and separating the component from the nozzle andmounting the same onto a predetermined mounting position of a circuitsubstrate by means of air blowing effect of the nozzle, in which themethod includes procedures for preventing occurrence of defectivesubstrates, which procedures comprise steps of; measuring air flowvolume blown from the nozzle at an air flow passage at a timingimmediately after completion of component mounting operation, which airflow passage is provided for supplying pressurized air to the nozzle;and making a judgment that the component has not been mounted onto thecircuit substrate, if the measurement value is smaller than apredetermined threshold.

It is also possible that the above method is to be arranged to comprisetwo thresholds, and said procedures comprise steps of: making a judgmentthat the component has not been mounted onto the circuit substrate, ifthe measurement value is smaller than both of the thresholds; and makinga judgment that the component has been mounted onto the circuitsubstrate, but that a filter disposed at the air flow passage isclogged, if the measurement value is in between the two thresholds. Inthis case, it is also possible that the procedures are to be arranged tocomprise steps of: measuring blowing air flow volume at two differenttimings immediately after completion of component mounting operation;making a judgment whether or not the component has been properly mountedonto the circuit substrate based on the first measurement value; andmaking a judgment either the component has been mounted onto the circuitsubstrate but the filter is clogged, or the component has not beenmounted onto the circuit substrate based on the second measurementvalue.

Yet another aspect of the present invention relates to a method ofcomponent mounting including procedures for preventing occurrence ofdefective substrates, which procedures comprise steps of; measuringdifferential of air flow volume blown from the nozzle at an air flowpassage at a timing immediately after completion of component mountingoperation, which air flow passage is provided for supplying pressurizedair to the nozzle; and making a judgment that the component has not beenmounted onto the circuit substrate, if the differential of air flowvolume decrease obtained by the measurement is bigger than apredetermined threshold.

The above method may also be arranged to comprise two thresholds, andthe procedures comprise steps of making a judgment whether a filterdisposed at an air flow passage is clogged or not, in addition to makinga judgment whether the component has been mounted or not. The proceduresmay also be arranged to perform the above measurement at two differenttimings, and utilize the measurement results for making the abovedescribed judgments.

Yet another aspect of the present invention relates to a method ofcomponent mounting including procedures for preventing occurrence ofdefective substrates, which procedures comprise steps of; measuringblowing air pressure blown from the nozzle at an air flow passage at atiming immediately after completion of component mounting operation,which air flow passage is provided for supplying pressurized air to thenozzle; and making a judgment that the component has not been mountedonto the circuit substrate, if the measurement value is bigger than apredetermined threshold. The above aspect is also possible to bearranged to comprise two thresholds for making a judgment of filterclogging, and/or to perform measurement at two timings in order toutilize measurement results for making judgments.

Yet another aspect of the present invention relates to a method ofcomponent mounting including procedures for preventing occurrence ofdefective substrates, which procedures comprising steps of; measuringdifferential of blowing air pressure blown from the nozzle at an airflow passage at a timing immediately after completion of componentmounting operation, which air flow passage is provided for supplyingpressurized air to the nozzle; and making a judgment that the componenthas not been mounted onto the circuit substrate, if the differential ofblowing air pressure decrease obtained by the measurement is smallerthan a predetermined threshold. The above aspect is also possible to bearranged to comprise two thresholds for making a judgment of filterclogging, and/or to perform measurement at two timings in order toutilize measurement results for making judgments.

Yet another aspect of the present invention relates to a method ofcomponent mounting including procedures for preventing occurrence ofdefective substrates, which procedures comprise steps of; measuringeither one of blowing air flow volume, differential of blowing air flowvolume decrease, blowing air pressure, or differential of blowing airpressure decrease of the air blown from the nozzle at an air flowpassage at a timing immediately after completion of component mountingoperation, which air flow passage is provided for supplying pressurizedair to the nozzle; comparing the result of the measurement with apredetermined corresponding threshold; making a judgment that thecomponent has been separated from the nozzle and mounted onto thecircuit substrate properly, if the blowing air flow volume or thedifferential of blowing air pressure decrease is bigger than thecorresponding predetermined threshold, or the differential of blowingair volume decrease or blowing air pressure is smaller than thecorresponding predetermined threshold, and then performing next roundcomponent pick up operation; making a judgment that the component hasnot been separated from the nozzle and that the circuit substrate ismissing the component, if the blowing air flow volume or thedifferential of blowing air pressure decrease is smaller than thecorresponding predetermined threshold, or the differential of blowingair volume decrease or blowing air pressure is bigger than thecorresponding predetermined threshold; stopping the component mountingapparatus; checking the nozzle, removing the component carried by thenozzle, and confirming that the nozzle is in a proper condition; andrestarting the component mounting apparatus for next round componentpick up operation.

The above method may also be arranged to comprise two thresholds, andthe procedures comprise steps of making a judgment whether a filterdisposed at an air flow passage is clogged or not, in addition to makinga judgment whether the component has been mounted or not. The proceduresmay also be arranged to perform the above measurement at two differenttimings, and utilize the measurement result for making the abovedescribed judgments.

Another aspect of the present invention relates to a component mountingapparatus comprising: component supply for supplying componentcontinuously; a mounting head having nozzles for picking up componentsfrom the component supply by means of air sucking effect, and separatingand mounting the components onto predetermine respective mountingpositions of a circuit substrate by means of air blowing effect; asubstrate holder for transporting and positioning the circuit substrate;an air sucking/blowing mechanism connected to the nozzles for providingair sucking effect and air blowing effect to the nozzle; and acontroller for controlling overall operations of the component mountingapparatus, in which the air sucking/blowing mechanism further comprises:either one of a measuring meter capable of measuring blowing air flowvolume or differential of the blowing air flow volume, or a pressuremeter capable of measuring blowing air pressure or differential of theblowing air pressure, either one of which is disposed at an air flowpassage for supplying pressurized air to the nozzle, and for measuringeither blowing air volume or pressure at a timing immediately aftercompletion of blowing air; and a controller for comparing the measuringresult obtained by either one of the meters with a correspondingpreliminary inputted threshold, and for making a judgment whether or notthe component has been mounted properly.

The above described component mounting apparatus may be arranged tocomprise two thresholds, and the controller may be designed to make ajudgment whether or not the component has been mounted properly or notbased on comparison between the measurement result and the firstthreshold, and/or making judgment either the component has been mountedonto the circuit substrate but the filter is clogged, or the componenthas not been mounted onto the circuit substrate based on comparisonbetween the measurement result and the second threshold.

The above described component mounting apparatus may be arranged tomeasure either one of blowing air flow volume, differential of blowingair flow volume decrease, blowing air pressure or differential ofblowing air pressure decrease at two different timings immediately afterair blowing operation; and the controller may be arranged to make ajudgment whether or not the component has been properly mounted onto thecircuit substrate based on comparison between the first measurementresult and the corresponding first threshold, and making a judgmenteither the a filter disposed at air flow passage is clogged, or thecomponent has not been mounted, based on comparison between the secondmeasurement value and the corresponding second threshold.

As described above, according to the procedures of detecting a nozzlewithout holding a component of the present invention, the componentmounting apparatus having a plurality of nozzles connected to a singlevacuum generating source may prevent occurrence of defective circuitsubstrates due to component loss which may be reliably detected withoutbeing affected by variance of achieved vacuum pressure after componentpick up. According to the present invention, it is also possible toprovide sufficient sucking power for sucking and holding a largercomponent, since a single vacuum source which generates higher vacuumpressure may be used. A single vacuum source arrangement may contributeto reduced cost, too.

Furthermore, according to the procedures of detecting component carryback by the nozzle of the present invention, it is possible to preventoccurrence of defective circuit substrates by detecting component carryback immediately after completion of component mounting operation.Therefore, according to a method and/or apparatus for mountingcomponents of the present invention, it becomes possible not only toprevent occurrence of defective circuit substrates due to misjudgment ofcomponent carry back, but also to improve productivity by avoidingsucking problems at component pick up stage due to interference by acomponent which has been carried back by the nozzle. It becomes alsopossible to prevent component pick up failure and to improve componentmounting quality by preventively detecting clogging of a filter disposedin the nozzle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective view of an embodiment of the componentmounting apparatus according to the present invention,

FIG. 2 shows a block diagram of a control system used for the componentmounting apparatus shown in FIG. 1,

FIG. 3 shows a circuit diagram of air pressure system used for thenozzle of the mounting head,

FIG. 4 shows connecting relations between nozzles and vacuum line,

FIG. 5 shows a flow chart of procedures for component loss detectionaccording to the present invention performed under the control of acontroller,

FIG. 6 shows an operation performed by a mounting head,

FIG. 7 shows an effect achieved by initializing the achieved vacuum tozero,

FIG. 8 shows a principle for making a judgment whether a nozzle isholding a component or not based on an absolute value of achieved vacuumpressure,

FIG. 9 is a block diagram showing a structure of air sucking/blowingsystem used for another embodiment of a component mounting apparatusaccording to the present invention,

FIG. 10 shows an outline of mounting failure detection procedures bymeans of the air sucking/blowing system shown in FIG. 9,

FIG. 11 shows another aspect of mounting failure detection proceduresshown in FIG. 10,

FIG. 12 is a flowchart showing mounting failure detection proceduresshown in FIG. 11 to be performed under control of a controller,

FIG. 13 is a flowchart showing alternative mounting failure detectionprocedures shown in FIG. 12,

FIG. 14 shows an alternative aspect of the mounting failure detectionprocedures shown in FIG. 11,

FIG. 15 shows yet another alternative aspect of the mounting failuredetection procedures shown in FIG. 11,

FIG. 16 is a flow chart showing mounting failure detection procedures tobe processed by the controller,

FIG. 17 is a flow chart showing procedures to be processed by thecontroller at an alternative aspect of the mounting failure detectionprocedures as shown in FIG. 11,

FIG. 18 shows outline of a method for detecting component loss in priorart, and

FIG. 19 shows a method of detecting mounting failure due to componentcarrying back in prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of a method and apparatus for mounting componentsaccording to the present invention will now be described by referring toappended drawings. The first embodiment of the present invention relatesto a method and apparatus of mounting components having procedures ormeans for detecting component loss by the nozzles. FIG. 1 shows anoverall view of a component mounting apparatus according to the presentembodiment. Referring to FIG. 1, the component mounting apparatus 100has a loader 7 for loading circuit substrates 5 into the componentmounting apparatus 100, which is located at right hand side in Xdirection of basement 3. Opposing to the loader 7 at left hand side in Xdirection, the component mounting apparatus 100 has an unloader 9 forunloading circuit substrates from the component mounting apparatus 100.Each of the loader 7 and unloader 9 has a pair of guide rails 11 and 13respectively arranged for transporting the circuit substrate 5.

A first substrate holder 15 a having support rails for transporting thecircuit substrate 5 is provided to the basement 3 facing to the loader7. Similarly, a second substrate holder 15 b having support rails fortransporting the circuit substrate 5 is provided to the basement 3facing to the unloader 9. The component mounting apparatus 100 shown inFIG. 1 comprises two mounting stages connected with each other inseries, and mounting operations may be performed on two circuitsubstrates 5 simultaneously at these two stages.

A pair of Y axis robots 17 are disposed along Y axis at both ends of thebasement 3 in X direction. First X axis robot 19 a and second X axisrobot 19 b are mounted on both Y axis robots 17 so as to be moved in Ydirection horizontally. Mounting heads 23 are mounted on both X axisrobots 19 a and 19 b respectively, which mounting heads 23 may be movedin X-Y directions and positioned in mounting operation area. These Xaxis robots 19 a and 19 b as well as Y axis robots 17 constitute a XYrobot 20, which is a transportation means for moving the mounting head23 in both X and Y directions together with a driving mechanism, e.g.,ball screw and nut, or belt driver.

A plurality of nozzles 25 which function as sucking and holding meansfor holding components are detachably attached to each mounting head 23.Component supplies 31 are formed at both ends of the basement 3 in Ydirection. The component supplies 31 may detachably hold componentsupply devices 29, such as component cassettes. Part trays 33 are alsoprovided in the vicinity of the component supplies 31, which may be usedfor supplying larger components (e.g., connectors or ICs such as ballgrid allay (BGA) or quad flat package (QFP)). Also in the componentmounting area close to the component supply 31, nozzle station 35 isprovided for stocking a variety of nozzles to be replaced uponnecessity.

Recognition camera 37 is positioned in the vicinity of the componentsupply 31 for imaging a component held by the nozzle 25. Also providedinside the component mounting apparatus 100 is a controller forrecognizing and controlling the component supply device 29. A monitorsuch as liquid crystal panel or CRT, indicating means such as warninglump, inputting means such as touch panel or key board are also providedat the front side of the component mounting apparatus 100.

FIG. 2 is a block diagram showing electric control system forcontrolling major elements of the component mounting apparatus 100 shownin FIG. 1. Referring to FIG. 2, the controller 41 is electricallyconnected with major elements such as loader 7, substrate holder 15(including the first and second substrate transport rails 15 a and 15b), unloader 9, XY robot 20 comprising X axis robots 17 and Y axisrobots 19 a and 19 b, component supply 31, and component recognitiondevice (recognition camera) 37. The controller 41 is also connected withdata base 43, driving system of mounting head 23, electromagnetic valvesof the nozzles 25, pressure sensor 50, pressure control valve 52, vacuumpressure supply source 60, etc. In the database 43, data such ascomponent library 43 a, NC program 43 b, substrate data 43 c and nozzledata 43 d, etc. are stored.

FIG. 3 is a circuit diagram showing a structure of air pressure controlsystem used for the nozzles 25 attached to the mounting head 23. Themounting head 23 is provided with first electromagnetic valves 71 forsucking system T1 and second electromagnetic valves 72 for blowingsystem T2 for respective nozzles 25. Each nozzle 25 is connected tovacuum line 75 via the first electromagnetic valve 71, and alsoconnected to blowing line 76 via the second electromagnetic valve 72.Sucking system T1 is provided for sucking and picking up a componentwith the nozzle 25, and blowing system T1 is provided for separating thecomponent from the nozzle 25 when mounting the component onto thecircuit substrate.

Negative pressure (vacuum) in the vacuum line 75 and positive pressurein the blowing line 76 are both generated by a single air pressuresource (air blower) 79 having air pressure control unit 78. Namely,upstream of the blowing line 76 is directly connected to the airpressure control unit 78 through a regulator 74, and pressurized airoutputted from the air pressure control unit 78 is directly supplied tothe blowing line 76. On the other hand, upstream of the vacuum line 75is connected to the air pressure control unit 78 via an ejector 77 and aregulator 73. Vacuum pressure may be generated by blowing pressurizedair into the ejector 77, and generated vacuum is supplied to the vacuumline 75. In other wards, the air pressure control unit 78 and air supplysource 79 are commonly used as a vacuum supply source as well as apressurized air supply source.

A pressure sensor 80 is connected to the vacuum line 75 for detectingvacuum pressure. As shown in FIG. 4, vacuum air passage 84 of the nozzle25 is connected to the vacuum line 75 through manifold 82, and the firstelectromagnetic valve 71 described above is provided for controllingsucking operation in the vacuum air passage 84, which valve 71 may openand close the vacuum air passage 84. A plurality of nozzles 25 arearranged linearly along the manifold 82, and the pressure sensor 80 ispositioned around the center of the nozzle arrangement of the manifold82. This arrangement may prevent the pressure sensor 80 from beingaffected by local pressure change due to component pick up failure byany one of the nozzles 25.

Now a method for mounting components comprising procedures for detectingcomponent loss to be performed at controller 41 (see FIG. 2) isdescribed. In this component mounting apparatus 100, a plurality ofnozzles 25, which are connected to a single vacuum generating sourcethrough the vacuum line, pick up and hold components and then mount thesame on the predetermined position of a circuit substrate. Sequence ofsuch operations is to be described by referring to a flow chart shown inFIG. 5.

After the process flow starts, the mounting head 23 moves to thecomponent supply 31, and the nozzle 25 attached to the mounting head 23picks up a component at step #1. When sucking a component, vacuumpressure is introduced to the nozzle 25 through the vacuum line 75 byoperating the first electromagnetic valve 71 provided to each nozzle 25.Wait for a while until vacuum pressure in vacuum line 75 becomes stableafter sucking a component by the nozzle 25, and when the vacuum pressurebecomes stable, a value of vacuum pressure is detected by the pressuresensor 80. At step #2, the detected value or the achieved vacuumpressure (absolute value) is checked whether it is higher than apredetermined threshold (second threshold, as an example here, 30 kPa).

When the achieved vacuum pressure is less than the threshold or 30 kPa,it may be judged that at least any one of the nozzles has failed to pickup a component, and vacuum is leaking from that particular nozzle. Inthis circumstance, component recognition scanning is performed at step#3. More specifically, the mounting head 23 is moved to the positionwhere the recognition camera 37 is located, and when the mounting head23 passes over the recognition camera 37, each of the nozzles 25 areimaged. The nozzle 25 that has failed to pick up a component may beidentified based on the imaged data. When such failed nozzle 25 isidentified, the first electromagnetic valve 71 of that particular failednozzle 25 is shut so as to prevent air leakage. Through such procedure,vacuum pressure in the vacuum line 75 may be recovered, and stablevacuum pressure condition at other nozzles 25 may be achieved.

Through performing procedures of steps #3 and #4 as described above, thenegative effect caused by component loss at component pick up stage maybe resolved. When the achieved vacuum pressure after component pick upoperation is more than 30 kPa at step #2, or when performing theprocedure at step #4 has been completed even after lower than 30 kPa ofachieved vacuum pressure has been detected, the flow goes to step #5where component recognition scanning is performed. Namely, each nozzle25 is imaged by the camera 37 when the mounting head 23 passes over therecognition camera 37, and condition of each nozzle 25 is recognizedbased on the imaged data. Component loss due to movement of the mountinghead 23 may be detected through these procedures.

At step #6, the achieved vacuum pressure is initialized to zero, andthen at step #7, the mounting head is moved to a position where mountingoperation is to be performed. Then, possible component loss which mayoccur after the procedures of identifying failed nozzle 25 is detectedat step #8, and judgment as to whether any component is lost or not ismade at step #9.

The procedures for making a judgment whether or not a component is lostare as follows. Vacuum pressure decrease from the initialized zero point(relative value) at nozzle 25 is measured, and if the measured pressuredecrease is bigger than the predetermined first threshold, it may bejudged that component has been lost. In such a case, at least thisparticular failed nozzle 25 is arranged to skip component mountingoperation. One possible way is to stop the component mounting apparatus(step #11). On the other hand, when vacuum pressure decrease from theinitialized zero is smaller than the first threshold, it may be judgedthat the is not component lost and that scheduled component mountingoperation may be performed (step #10).

FIGS. 6A-6D show relations between movement of the mounting head 23 andthe recognition camera 37. Referring to FIG. 6, after completion ofcomponent pick up operation, the mounting head 23 moves over therecognition camera 37 as shown in FIGS. 6A and 6B, and during suchmovement, condition at each nozzle 25 is imaged and recognized by thecamera 37. When the achieved vacuum pressure after completion ofcomponent pick up operation is lower than 30 kPa, the failed nozzle 25or the nozzle 25 that has failed component pick up is identified. Inthis case, vacuum passage to the failed nozzle 25 is shut so that vacuumpressure in the vacuum line 75 may be recovered.

Next, the mounting head 23 is raised to normal height as shown in FIG.6C, and the head 23 is moved toward a position where a circuit substrateis located, during which timing such height is normally maintained.However, there is a possibility that a component held by the nozzle 25may be lost due to, for example, movement shock of the mounting head 23.If a component is lost, this may be detected, as explained above, bymeasuring vacuum pressure decrease, since there should be vacuumpressure decrease from the initialized achieved vacuum pressure(base=zero) due to component loss. When component loss is found, onepossible solution may be stopping the component mounting apparatus asdescribed above, but another possible way is to move the mounting head23 over the recognition camera 37 one more time as shown in FIG. 6D, andto identify from which nozzle 25 a component has dropped. Through suchprocedures, it becomes possible to perform component mounting operationby the nozzles 25 other than by the identified failed nozzle 25.

As explained above, the controller 41 makes two kinds of judgment basedon detected vacuum pressure. One judgment is to find out, by using theachieved vacuum pressure as an absolute value, component pick up failureat component pick up stage based on whether or not the absolute value isbigger than the second threshold (30 kPa). Another judgment to be madeis to find out, by using initialized achieved vacuum pressure aftercompletion of component pick up operation, component loss from thenozzle during movement of the head 23 based on whether or not therelative vacuum pressure decrease from the base value (zero) is biggerthan the first threshold value.

For these reasons, analog outputs to be transmitted to the controller 41are inputted into two separated channels CH1 and CH2 disposed on thecontroller 41, and the outputs are processed both at CH1 and CH 2,separately.

In the process performed at CH1, the achieved vacuum pressure isinitialized to zero after vacuum becomes in stable condition. Throughthis procedure, the pressure achieved at completion of component pick upoperation under any sucking conditions would be initialized to zero,thereby variance of achieved vacuum pressure after component pick upwould not cause any influence upon future detection. Under suchcondition, if air leakage due to component loss occurs and vacuumpressure change due to such leakage becomes bigger than the firstthreshold (10 kPa, for example), it may be judged that a component islost, and an alarm signal may be generated for warning an operator. Inbrief, any changes of component condition after completion of componentpick up operation may be monitored through the process performed at CH1.If component loss is detected during the course, as stated above, it maybe possible either to stop the component mounting apparatus or to skipcomponent mounting operation with that particular failed nozzle.

In the process performed at CH2 on the other hand, the achieved pressureafter completion of component pick up operation would not be initializedto zero, but rather the achieved pressure is monitored as an absolutevalue. If the achieved vacuum pressure after completion of componentpick up operation is lower than the predetermined second threshold value(30 kPa, for example) the controller transmits a signal to warn thatsucking power is low. In brief, pressure condition after completion ofcomponent pick up is monitored in the process performed at CH2.

The above mentioned effects will be explained in more detail byreferring to FIGS. 7 and 8. Vacuum pressure pattern during componentpick up may vary depending upon configuration of component etc., henceachieved vacuum pressure may vary as exemplarily shown in pattern 1-3 inFIG. 7. However, if the achieved vacuum pressure is initialized to zero,and by checking pressure change (vacuum pressure decrease) base on thatinitialized standard, component loss may be detected by using a singlethreshold P1 without being influenced by such achieved vacuum pressurevariance.

When component loss is detected based on such relative vacuum pressurechange, it becomes possible to prevent occurrence of defective substrateby simply skipping component mounting operation by that particularfailed nozzle 25. Furthermore, when component loss is detected,component mounting operation by the nozzles 25 other than thatparticular failed nozzle 25 may by performed, whereby unnecessary wasteof components held by the nozzles without failure may be saved if thefailed nozzle 25 is identified through performing recognition processagain.

In the process performed at CH2 as shown in FIG. 8, achieved vacuumpressure at completion of component pick up operation is detected as anabsolute value, and whether component pick up is properly performed (OK)or not (NG) may be judged by comparing measurement value with the secondthreshold P2 (e.g., 30 kPa), hence countermeasure may be takeninstantly. That is, the nozzle 25 that failed component pick up andvacuum air is leaking may be identified by imaging the nozzles 25 withthe recognition camera 37, and the vacuum air passage 84 of thatidentified failed nozzle 25 may be shut so as to recover overall vacuumpressure.

The above mentioned first threshold (:10 kPa) and second threshold (:30kPa) used at CH1 and CH2 may be determined at any appropriate values byconsidering achieving pressure of the vacuum pressure supply and/orrouting of pipes etc. As the second threshold is to be determined basedon relations between the achieved vacuum pressure and a number ofcomponent losses as shown in FIG. 8, it would be preferable to set thesecond threshold at around 30 kPa level. If the threshold is set lowerthan this level, it would be difficult to identify a number of componentlosses due to minimized pressure change corresponding to a number ofcomponent losses.

It may be possible to provide an orifice in the vacuum air passage 84for protecting air leakage from the failed nozzle 25. In this case,smaller area of air flow in the orifice helps preventing rapid pressuredecrease.

Now the second embodiment of a method and apparatus for mountingcomponents according to the present invention having procedure and meansfor detecting mounting failure and component carrying back by the nozzleafter completion of mounting operation will be described by referring toappended drawings. In the following embodiments, the like elements asexplained in the first embodiment will bear like reference numerals.Configuration of the component mounting apparatus is basically the sameas the one described by referring to FIGS. 1-3 in the first embodiment.The following description is basically focused on differences betweenthe present embodiment and the prior art and/or the first embodiment.

FIG. 9 shows outline of an air sucking/blowing mechanism 10 of thepresent embodiment, which may be used for supplying vacuum pressure tothe nozzle 25 for sucking a component, and pressurized air to the nozzle25 for separating a component. The air sucking/blowing mechanism 10 isdesigned to provide the nozzles 25 of the mounting head 23 withsucking/blowing effect. The air sucking/blowing mechanism is connectedto a nozzle 25 through a connection tube 18. Referring to FIG. 9, theair sucking/blowing mechanism 10 comprises: a regulator 73 (whichincludes the ejector 77 as shown in FIG. 3) to be connected to vacuumline 75 for supplying vacuum pressure to opening of the nozzle 25 duringcomponent sucking; a regulator 74 to be connected to blowing line 76 forsupplying pressurized air to the opening of the nozzle 25; a switchingmeans 70 such as electromagnetic valve for selectively switching thepassage to the nozzle 25 between the vacuum line 75 and the blowing line76; and a controller 41 for providing switching operation command to theswitching means 70 in synchronism with component mounting operation. Thecontroller 41 may be integrated into the controller of the componentmounting apparatus, or may be separated in which case controllingoperation of the controller 41 needs to be in synchronism withoperations of the component mounting apparatus. The regulators 73 and 74are connected to the air pressure source 79 through air pressure controlunit 78 as shown in FIG. 3.

In the mounting head 23, an air flow passage 21 is provided forconnecting the connecting tube 18 and the nozzle 25, and a filter 22 forfiltering dusts or debris is placed in the air flow passage 21. Acomponent 30 is picked up by the nozzle 25 with the sucking effect ofvacuum which is provided through the vacuum line 75, and when mountingthe component, the switching mechanism 70 switches connection of thenozzle to the blowing line 76 so that the component 30 may be separatedfrom the nozzle 25 with positive air pressure generated by blowing airthrough blowing line 76.

In the air sucking/blowing mechanism 10 of the present embodiment,measuring meter 61 for measuring blowing air flow blown from the nozzle25 through the blow line 76 is attached to the blowing line 76, which isa passage for blowing air between the regulator 74 and the switchingmechanism 70. The controller 41 provides a command to the measuringdevice 61 to measure the blowing air blow volume at appropriate timing,in addition to providing a command to the switching means 70. Further,measuring data obtained by the measuring meter 61 is transmitted to thecontroller 41, and the controller 41 compares the data with thepreliminarily inputted threshold for making necessary judgment.

Although only one nozzle 25 is shown in FIG. 9, the vacuum pressuresupply source and the pressurized air supply source may be commonly usedby a plurality of nozzles which are attached to a single mounting head.The switching means 70 and the measuring meter 61 are to be provided foreach nozzle 25 separately. In FIG. 9, the mounting head 23 and the airsucking/blowing mechanism 10 are shown in separated positions, but theymay be integrated into the mounting head 23 as shown in FIG. 3. Further,single switching means (electromagnetic valve) 70 performs switchingoperation between vacuum pressure and positive pressure in theillustrated example in FIG. 9, but this may be arranged in a similarmanner as shown in FIG. 3 where both vacuum line and pressurized linehave independent electromagnetic valves 71 and 72.

Now a method for detecting mounting failure (component carrying back)according to the present embodiment using the air sucking/blowingmechanism 10 as described above will be explained by referring to FIGS.10A-10C. FIG. 10A shows movement of the nozzle 25 during the time elapseindicated in horizontal axis. In the drawing, the nozzle 25 transportsthe picked up component 30 by movement of the mounting head 30, andafter stopping at the position opposing to a circuit substrate 5, thenozzle 25 descends against the circuit substrate 5. The circuitsubstrate 5 is firmly placed at its position. The nozzle 25 reaches atits lowest position at the mounting timing T, which is shown in themiddle of the horizontal axis, and mounts the component 30 onto thecircuit substrate 5. After completion of component mounting, the nozzle25 moves upward and returns to the original position.

FIG. 10B shows blowing air flow volume (in vertical axis) flown throughthe nozzle 25 (hence through measuring meter 61 shown in FIG. 9) duringtime elapse corresponding to movement of the nozzle 25 (horizontal axis)as shown in FIG. 10A. The nozzle 25, which has been holding thecomponent 30 with sucking effect through vacuum line 75, separates thecomponent 30 when the switching means 70 of the air sucking/blowingmechanism 10 switches connection of the nozzle 25 to the blowing line76, and mounts the component 30 onto the circuit substrate 5. Due tosuch air blowing action, the blowing air flow volume reaches at its peakat mounting timing T, and then air blow volume gradually decreases. Themeasuring meter 61 provided to the air sucking/blowing mechanism 10measures blowing air flow volume at measuring timing S as shown in thedrawing, and transmits the measured data to the controller 41.

In practice, there is a small time elapse between the time when thenozzle 25 touches the circuit substrate 5 and separates the component30, and the time when the nozzle completes component mounting and startto ascend (e.g., about 20 ms). Also, in order to change vacuum conditionof the nozzle 25 for holding the component to positive pressurecondition by breaking such vacuum condition, there is also a small timeelapse (e.g., about 20 ms). These time elapses cause gradual air flowvolume increase even before the mounting timing T, as shown in FIG. 10B.Accordingly, actual mounting operation is performed during a time spanincluding such time elapses. In this specification, the timing when theblowing air flow volume reaches at its peak during component mountingoperation is referred to as the mounting timing T.

After completion of component mounting, the blowing air flow volumedecreases from the peak, and then the air flow volume would saturate ata certain constant level as shown in FIG. 10B. This is because, evenafter completion of component mounting, air blowing from the nozzle 25is continued at a certain volume level for the time being (e.g., about20 ms) until the mounting head 23 starts to move for next roundcomponent pick up operation. The measuring timing S for measuringblowing air flow volume is determined where the blowing volume saturatesat a certain level, or in the vicinity of thereof.

FIG. 10C shows comparison of result of the blowing air flow volumemeasured by the measuring meter 61 with a predetermined threshold. Whenthe component 30 is separated from the nozzle 25 and mounted properly,the blowing air flow volume changes along the pattern as shown by thecurve “proper mounting” in the drawing, and a certain volume of air flowis blown from the nozzle 25 since the opening of the nozzle 25 iscompletely cleared. On the contrary, if the component 30 is notseparated from the nozzle 25 for some reasons, and continued to be heldby the nozzle 25, the blowing air flow passing through the nozzle 25changes along the pattern as shown by the curve “component missing” inthe drawing, since the opening of the nozzle 25 is blocked by thecomponent 30 which is still held by the nozzle 25. There is a big gapbetween the two patters of “proper mounting” and “component missing”.The threshold may be determined base on statistic data of such volumedifference, and judgment as to whether the nozzle 25 has failedcomponent mounting and is carrying back the component may be made byusing the predetermined threshold.

The blowing air flow measuring timing S may be set immediately after themounting timing T (e.g., within 10 ms time interval), as shown in thedrawing. According to the present embodiment, the measuring device 61 isdisposed at blowing line 76 which is the air flow passage in the airsucking/blowing mechanism 10, and blowing air flow volume may bemeasured at any timing because it is not required to move the nozzle 25to a remote position where a measuring device is located as in the caseof prior art. Accordingly, it become possible to set measuring timing Sfar closer to mounting timing T than in the case of prior art. Moreover,no extra spaces are needed for blowing air flow measuring because themeasuring meter 61 may be disposed inside the air sucking/blowingmechanism 10, rather than outside of the nozzle 25 as in the case ofprior art.

Positioning the measuring meter 61 is not limited to at the blowing line76 as shown in FIG. 9, and the measuring meter may be disposed at otherlocations such as at connection tube 18, at air flow passage 21 or atany other air flow passage before it reaches to the nozzle 25.

Some exemplary reasons why the component 30 is not separated from thenozzle 25 are: penetration of cream solder into contacting interfacebetween the nozzle 25 and the component 30 when cream solder is appliedto the circuit substrate 5; deposit of adhesive materials on the nozzle25; condensation of moisture on the surface of the component 30, etc.

FIG. 11 shows another aspect of the method of detecting mounting failureaccording to the present embodiment. FIG. 11 basically corresponds toFIG. 10C, but two thresholds 1 and 2 are illustrated in FIG. 11, whichmay be used for making a judgment not only either “proper mounting” or“mounting failure”, but also whether or not the filter 22 (see FIG. 9)associated with the nozzle 25 is clogged.

When dusts or debris are accumulated in the filter 22 located in the airflow passage 21, the air flow volume passing the blowing line 76 isreduced due to blockage of the air flow by such dusts etc. Sizes ofthese dusts or debris are in μm orders, which are far smaller than thesizes of chip components. Accordingly, blocking effect by the dustsagainst air flow volume is also significantly smaller than that of thecomponent 30. Therefore, it is possible, by using statistic data, todistinguish whether the blocking effect is caused by clogging of thefilter 22 or by remaining component 30. Threshold values 1 and 2 may bedetermined based on respective statistic data, and they can be used formaking a judgment whether the nozzle 25 has “properly mounted” acomponent, or has failed to mount a component (“mounting failure”) orthe filter is clogged (“filter clogging”).

More specifically, two thresholds 1 and 2 are preliminary determinedbased on accumulated data, and the blowing air flow volume aftercompletion of component mounting are compared with these two thresholds.If the measuring result is bigger than both of the thresholds 1 and 2,it may be judged that the component has been properly mounted. If themeasuring result is smaller than both of the thresholds 1 and 2, it maybe judged that the component has not been mounted (mounting failure). Incase the measuring result is between the two thresholds 1 and 2, it maybe judged that the filter 22 is clogged. The term “proper mounting” usedin this specification is to mean that the component is mounted properlyby the effect of blowing air flown from the nozzle 25 without havingfilter clogging, and the term “clogging” is to mean that the filter 22is under clogged condition. Although it is referred to as “filterclogging” in the above description, it should be understood thatclogging of other portion such as clogging of blowing line 76,connection tube 18 or inside the nozzle 25 may also be detected by thesame procedures. Therefore, the term “filter clogging” is not limited toclogging of the filter itself, but clogging of other portions likedescribed above is also included.

When component carrying back by the nozzle 25 is detected, the component30 should be in a condition still being held by the tip of the nozzle25. If such particular nozzle 25 performs next round component pick upoperation, the component 30 still held by the nozzle 25 may interferethe pick up operation. Also, if no counter measures are taken aftermounting failure is detected, the circuit substrate 5 would be adefective product due to missing component. Therefore, it is desirableto provide necessary procedures in component mounting operations whichmay lead to avoid these kinds of undesirable situations.

The flow chart of FIG. 12 shows procedures of a method for mountingcomponent having procedures of detecting mounting failure according tothe present embodiment, as well as a counter measures for avoidingcomponent pick up failure as described above. The method also hasprocedures of countermeasures for recovering missing components so as toprevent occurrence of defective circuit substrate. The method ofcomponent mounting of the present embodiment is hereinafter described byreferring to FIG. 12.

Referring to FIG. 12, a nozzle 25 picks up a component 30 at step #1,and mounts the component 30 onto a circuit substrate at step #2. Blowingair flow volume is measured at step #3, and the measurement value iscompared with the threshold 1 at step #4. If the measurement value ofair flow volume is bigger than the threshold 1, the component 30 isjudged to have been properly mounted as shown in step #6, and, in thiscase, the process flow goes to step #7 for picking up next component 30,and repeating the procedures from step #2.

If the measurement value is smaller than the threshold 1 at step #4, theprocess flow goes to step #8, where the measurement value is comparedwith the threshold 2. If the measurement value is bigger than thethreshold 2, it may be judged that the filter is clogged at step #9. Inthis case, an alarm is generated for warning an operator at step #11,and the flow may go to step #7 for picking up next component 30. As thecomponent 30 is judged to have been properly mounted in this case, itmay not cause any problems even if the nozzle 25 with the clogged filterpicks up the next component 30. Nevertheless, the operator has an optionto stop the component mounting apparatus at step #12, and takesnecessary actions such as cleaning or replacing the nozzle 25 and/orfilter 22 at step #13. Then the operator may restart the componentmounting apparatus at step 14, and the process flow may goes to pickingup operation at step #7.

Now back to step #8, if the measurement value of air flow volume issmaller than the threshold 2, it is judged that the component has notbeen mounted (the nozzle 25 is carrying back the component 30) at step#15. In this case, the component being carried by the nozzle is to bediscarded at step #16 so as to avoid causing any problems at next roundcomponent pick up operation due to the remaining component 30.Specifically, the nozzle 25 is moved to component discarding position,where high pressure air is blown through that nozzle 25, or the nozzleopening is cleaned by using a blush or the like. In this circumstance,next round component pick up operation is skipped at step #17, andblowing air flow volume is measured again at step #18 in order tore-confirm that the component held by the nozzle has been discarded. Ifit is confirmed at step #19 that the measurement value is bigger thanthe threshold 1, which means that the component has been discarded, theflow goes to step # 21 to pick up the next component 30, and mount thesame for recovering the missing component during the previous roundmounting operation at step #15. These procedures are to be repeated.

If the measurement value at step #19 is smaller than the threshold 1, itis judged at step 22 that the component has not been discarded duringthe step #16, and that the nozzle is still carrying the component. Inthis case, the component mounting apparatus is stopped at step #23, andan operator takes necessary actions such as checking and cleaning thenozzle 25 at step #24, and then component mounting apparatus isre-started at step #25. At step #21, the next component is picked up,and then mounted on the same circuit substrate for recovering themissing component.

As the flow chart of FIG. 12 shows, it is preferable to re-confirmautomatically whether the carried back component has been discarded ornot, but alternatively these procedures may also be performed manually,i.e., an operator stops the component mounting apparatus and checks thenozzle visually. FIG. 13 shows a flow chart in which the aboveconfirmation procedures are performed manually. Referring to FIG. 13,steps #1-#14 are the same as the flow chart of FIG. 12. If mountingfailure is detected at step #15, an operator stops the componentmounting apparatus at step #31. At step #33, an operator visually checksthe condition of the nozzle 25, removes the component if it is stillbeing carried by the nozzle 25, and confirms that the nozzle 25 is inproper condition. Then the component mounting apparatus is restarted atstep #34, and next component is picked up and then mounted on thecircuit substrate for recovering the missing component at step #35.

In case of the flow charts shown in FIGS. 12 and 13, two thresholdvalues 1 and 2 as shown in FIG. 11 are used for detecting both mountingfailure and filter clogging. In case only the threshold 1 is used asshown in FIG. 10C, all the procedures from steps #8-#14 in FIGS. 12 and13 related to threshold 2 are not necessary. Also in case of the flowcharts shown in FIGS. 12 and 13, the nozzle 25 which has failedcomponent mounting is arranged to perform a recovering mountingoperation by mounting the same component (step #21 or #35), but suchrecovering may be performed by using a different nozzle, and the nozzlewhich has failed to mount a component may be used to mount a differentcomponent at the next round operation.

Although not shown in the flow chart of FIGS. 12 and 13, furtherprocedure for confirming whether the component is actually missing ornot may be performed. Such confirmation procedure may be performed bychecking the circuit substrate 5 either manually by an operator orautomatically by using a recognition means, after component missing isdetected at step #15. If component missing is confirmed by suchprocedure, it may be judged that the nozzle 25 has carried back thecomponent 30. On the other hand, if it is confirmed by this procedurethat the component 30 is properly mounted, it may be judged thatdetection made at step #15 was not correct, and that something wrongwith either measuring meter 61, nozzle 25 or filter 22.

As described above, according to the present embodiment, blowing airflow volume of a nozzle 25 immediately after completion of componentmounting operation may be measured by means of measuring meter 61deployed in air sucking/blowing mechanism 10 of a nozzle 25. By thisarrangement, phenomena of component carrying back may be reliablydetected, without worrying about a space for locating a measuring meter,and with reduced risk of making a misjudgment due to component lossduring a time lag between component mounting and measuring. Furthermore,by providing a plurality of thresholds properly, not only defectivesubstrate due to component missing, but also clogging of filter 22 maybe detected, hence it becomes possible to take preventive maintenanceactions so as to avoid component picking up failure and/or componentmounting failure due to clogging of a nozzle.

A variety of alternative aspects of the present embodiment of a methodfor detecting mounting failure due to component carrying back may beconceivable. FIG. 14 shows a first alternative aspect of the presentembodiment. In this aspect, blowing air flow from the nozzle 25 ismeasured at two different timings S1 and S2 immediately after completionof component mounting, for the purpose of improving detection quality.

As described above, component size is becoming smaller and smallerrecently, and blowing air flow measurement at measuring timing S (seeFIG. 10 a) may not be accurate enough for evaluating a difference fromthe threshold due to small opening area of recent small sized nozzles.It may be especially difficult to distinguish between filter cloggingand mounting failure due to so small amount of flowing air volume. Onepossible solution to overcome this problem may be to delay measuringtiming S until the blowing air flow becomes stable and such air flowdifference becomes clearer. However, if the measuring timing S isdelayed, the timing gap between mounting timing T and measuring timing Swould be longer, and this may cause negative effects such as lengtheningof operational cycle time due to the delayed timing, or increasing riskof making a misjudgment due to component missing during such time gap.

A method of detecting mounting failure and/or nozzle clogging accordingto the present embodiment may resolve those problems. Referring to FIG.14, first blowing air flow measurement is performed at measuring timingS1 immediately after the nozzle 25 has completed component mounting bymeans of air blowing. By comparing the result of measurement of theblowing air flow obtained at measuring timing S1 with the predeterminedthreshold 1, whether the component 30 is properly mounted on the circuitsubstrate 5 or not is detected, first. As shown in the drawing, “propermounting” may be detected even at such early measuring timing S1immediately after air blowing operation, because blowing air flow volumeis relatively large in the case of “proper mounting” compared to othercases. It is also possible to reduce a risk of making a misjudging dueto component loss because measuring may be done at such an early timingafter component mounting operation.

Then, the second measurement of the blowing air flow volume is conductedat measuring timing S2, in which the nozzle 25 has completed mountingoperation and starts to move upward. The tip of the nozzle 25 at thistiming is completely in cleared condition. Since the blowing air flow atthe measuring timing S2 is stable, it is relatively easy to identify inwhich area the blowing air flow volume is to be categorized. Bycomparing the measurement result with the threshold 2 at this timing, itmay be identified the reason why it was judged not properly mounted atthe first measuring timing, either because of “mounting failure” orbecause of “filter clogging”. Event this second measuring timing is muchcloser to mounting timing T compared to prior art, because moving thenozzle toward the detecting device or flow measuring meter is notrequired. Accordingly, it becomes possible to reduce a risk of making amisjudgment due to component loss during such movement.

The procedures of the present embodiment are substantially the same asthe flow chart shown in FIGS. 12 and 13, except blowing air flow volumeis measured at two different timings. Even for the case where a smallcomponent (e.g., chip component having a span length of less than 1.0mm) is to be mounted, or the case where small nozzle is used, anaccurate judgment may be made whether the result situation is “propermounting”, “nozzle clogging” or “mounting failure” by measuring blowingair flow at two different timings. This may help preventing occurrenceof defective substrate and improving quality of component mountingoperation.

FIG. 15 shows a second alternative aspect of the present embodiment, inwhich variance of blowing air flow volume is measured instead of blowingair flow volume. In this aspect, the measuring meter 61 of the airsucking/blowing mechanism 10 shown in FIG. 9 is designed to calculatevariance (differential or derivative) of blowing air flow volume bymeasuring blowing air flow volume for a certain length of time andprocessing the obtained data. Other structure of the air sucking/blowingmechanism 10 is the same as those described above.

The pattern of blowing air flow passing through the nozzle shown in FIG.15 is the same as the one shown in FIG. 11. In this aspect of theembodiment, the measuring meter 61 deployed at blowing line 76calculates differential of the blowing air flow passing through thenozzle 25 at measuring timing S, which is immediately after completionof component mounting. Blowing air flow volume at such measuring timingS is in decreasing stage after mounting operation, hence thedifferential (derivative) of the blowing air flow may be shown indowngrading inclination in a graph. When illustrating such inclinationmeasured at appropriate measuring timing S, as shown by divided lineswith two dots in FIG. 15, the inclination for the case of “propermounting” is relatively gentle, since air flow from the nozzle is quiteeasy after separation of the component, the inclination for the case of“mounting failure” is relatively steep, since blowing air flow decreasesrapidly due to blockage by the held component. In case the component hasbeen mounted but the nozzle is clogged, the level of inclination will bemedial between the two previous inclinations.

By inputting such inclinations into the controller 41 as thresholds (notshow in the drawing), judgment may be made either the case is to becategorized in “proper mounting”, “nozzle clogging” or “mountingfailure” by comparing calculated inclination (derivative) of the casewith these thresholds. Although two thresholds are used for detectingnot only “mounting failure” but also “filter clogging” in FIG. 15,single threshold may also be used for detecting “mounting failure” only.In addition, FIG. 15 shows a case the blowing air flow is measured atonly one measuring timing S, but measuring blowing air flow at twodifferent timings as shown in FIG. 14 may also be possible for thepurpose of improving measurement accuracy.

Dotted line A in FIG. 15 shows a second measuring timing in the case ofthe embodiment shown in FIG. 11. As is explained before, if blowing airflow volume itself is used as a basis for making judgment, certain timespan is needed to wait until the time when air flow becomes stable. Onthe contrary, according to the present embodiment where differential ofblowing air flow volume is used, measurement timing S may be set evencloser to mounting timing T, and this may help avoiding making amisjudgment due to component loss during such timing gap, and improvingcomponent cycle time.

Flow chart of FIG. 16 shows procedures of the alternative aspect of thepresent embodiment as described above. The procedures shown in FIG. 16are basically similar to those of the flow chart shown in FIGS. 12 and13. The difference lies in that differential of blowing air flow ratherthan blowing air flow is measured at step #3. Also in step #4 and #5,obtained differential of air flow (inclination of air flow decrease) iscompared with thresholds 1 and 2, and judgment is made whether theobtained differential is smaller or not than the thresholds 1 and 2,rather than bigger or not as in the case of previous embodiment. Otherprocedures are the same as those of the previous embodiment.

As explained before, the component mounting apparatus in prior artgenerally adopts a system in which blowing air flow continues for awhile after completion of component mounting until the time the mountinghead 23 starts to move. Recently, in some type of component mountingapparatus, it is designed to shut such wasting of unnecessary airblowing at earlier timing by adding an electromagnetic valve. Accordingto the present embodiment, mounting failure may be detected even in suchtype of component mounting apparatus, since detection may be performedat very early stage immediately after component mounting, and waitingfor stable air flow condition is not required.

Now the 3rd aspect of the present embodiment of a method of detectingmounting failure is hereinafter described. In this embodiment, pressureof blowing air flow, rather than blowing air flow volume as in the caseof previous embodiments is measured. Toward this end, among the elementsforming the air sucking/blowing mechanism 10 shown in FIG. 6, referencenumeral 61 is to be a pressure meter designed to measure pressure of theblowing air flow rather than air flow volume. Other structures of theair sucking/blowing mechanism 10 are the same as those of theembodiments explained so far.

As explained, when an opening of the nozzle 25 is blocked by a component30, or when the filter 22 is clogged by dusts and/or debris, air flowvolume is reduced since these obstacles may hinder air flow. When theair flow is blocked and air flow volume changes, the pressure inside airsupply passage also changes simultaneously due to choking effect bythese obstacles. By detecting such pressure changes, “proper mounting”,“mounting failure” or “filter clogging” may be judged in a similarmanner as the previous embodiments.

The nozzle 25 is in vacuum condition when sucking a component. At thetime mounting a component, air pressure inside the nozzle 25 increasesso as to blow air, and when mounting operation is completed and thecomponent 30 is separated, the pressure inside the nozzle 25 graduallydecreases. After the component 30 has been mounted properly, pressureinside the nozzle 25 rapidly decreases since the component 30 has beenseparated from the nozzle 25 by the effect of blowing air, and thenozzle opening is completely uncovered. On the contrary, in case of“mounting failure (the nozzle 25 carries back a component)”, thecomponent 30 carried by the nozzle 25 blocks the nozzle opening andblowing air flow is limited, hence pressure drop in blowing line 76 isno so rapid. In case of “nozzle clogging”, the pressure would be inmedial level between the above two cases. Accordingly, by comparingmeasured pressure data and the thresholds 1 and 2 selectively determinedbased on statistics data, either “proper mounting”, “filter clogging”,or “mounting failure” may be judged effectively in a similar manner asthe previous embodiments.

As in the case of previously described other embodiments, the timing formeasuring blowing air pressure of the nozzle 25 may be arranged attiming very close to mounting timing in the present embodiment too.Accordingly, a risk of making a misjudgment due to component loss duringmeasuring timing delay may be reduced. It is also possible, as in thecase of embodiment as shown in FIG. 14, measuring of air pressure may beperformed at two different timings immediately after completion ofcomponent mounting, and these measured data may be used for making moreaccurate judgment. It is more beneficial to employ such two timingmeasurement method especially in the case where small nozzle 25 is used.

The flow chart of FIG. 17 shows procedures of detecting mounting failureof the present embodiment. The procedures shown in FIG. 17 are basicallysimilar to those in the flowchart shown in FIGS. 12 and 13, except step#3 where blowing air pressure rather than volume is measured. Otherdifference lies in steps #4 and #8, where measured data are comparedwith threshold 1 and 2, and the judgment is to be made based on whetherthe measurement value is smaller or not than the threshold 1 and 2,rather than bigger or not. Other procedures are the same.

In the above explanation, a pressure meter is used as an alternative ora replacement of a measuring meter used for measuring blowing air blowvolume in the previous embodiments, but both air volume measuring meterand air pressure measuring meter may be used together so as to improvejudgment quality and to make a comprehensive judgment by usingmeasurement data obtained from both of the measuring devices.

Further, in the above explanation, measured result of air pressure isused for making a judgment of mounting failure etc., but it is alsopossible to obtain variance (differential or derivative) of air pressurechange in a similar manner as the case of the second alternative aspectshown in FIG. 15, and to make a judgment of mounting failure etc. usingthe result data of inclination of pressure decrease for comparing withcorresponding threshold. In this case, steeper inclination is to bejudged as “proper mounting”, gentler inclination is to be judged as“mounting failure”, and medial inclination is to be judged as “filterclogging”. The measuring meter 61 in this case is designed to measureair pressure for a certain length of time, and process the measured datafor obtaining pressure differential.

A method and an apparatus for mounting components having means andprocedures for detecting mounting failure or component pick up failureby the nozzle has been described, but the scope of the present inventionis not limited to those embodiments. For example, FIG. 1 shows acomponent mounting apparatus of a type having XY robot for transportingthe mounting head in both X and Y directions, but the present inventionmay also be applied to different types of component mounting apparatus,such as the one having Y robot in which mounting head may be transportedonly in Y direction, or a rotary type component mounting apparatuscomprising an index capable of rotating a plurality of nozzlesintermittently.

While it is beneficial to employ both of the means or procedures fordetecting component pick up failure by the nozzle according to the firstembodiment, and means or procedures for detecting mounting failure dueto component carrying back by the nozzle for avoiding occurrence ofdefective substrate, but it should be noted that these embodiments maybe performed independently.

1. A method of component mounting for picking up components and mountingthe same onto respective predetermined mounting positions of a circuitsubstrate by means of a plurality of nozzles connected to a singlevacuum generating source, wherein the method including procedures forpreventing occurrence of defective circuit substrates due to missingcomponent, said procedures comprising steps of: initializing achievedvacuum pressure of a nozzle after completion of component pick upoperation to zero; detecting vacuum pressure decrease of the nozzle fromthe initialized zero value; and if the detected vacuum pressure decreaseexceeds predetermined first threshold, making a judgment that the nozzlehas failed to pick up a component, and skipping component mountingoperation by that particular nozzle.
 2. The method according to claim 1,further comprising steps of: before initializing the achieved vacuumpressure of a nozzle to zero, detecting absolute value of the vacuumpressure achieved by the nozzle after completion of component pick upoperation, and if the detected achieved vacuum pressure is lower thanpredetermined second threshold, shutting a vacuum air passage of thatparticular nozzle.
 3. The method according to claim 2, furthercomprising steps of: imaging each of the nozzles with a recognitioncamera; and identifying which nozzle has failed to pick up a componentbased on the obtained images.
 4. The method according to claim 3,further comprising steps of: after identifying the nozzle that hasfailed to pick up a component based on the obtained images, shutting avacuum air passage of that identified nozzle; imaging the identifiednozzle one more time, and detecting whether or not a component is stillcarried by the nozzle.
 5. The method according to claim 2, wherein thenozzles perform component mounting operations, excluding the nozzle thatis judged to have failed to pick up a component and the nozzle whosevacuum air passage is shut.
 6. Component mounting apparatus comprising:a vacuum generating source; a plurality of nozzles connected to saidvacuum generating source, each of which nozzles has a control valvecapable of shutting a vacuum air passage; a mounting head beingsupported in a movable manner and holding said plurality of nozzles; acomponent recognition device positioned to face with the mounting headfor recognizing components held by the nozzles; and a controller forcontrolling operations of the component mounting apparatus in accordancewith a method according to any one of the preceding claims.
 7. A methodof component mounting for picking up a component by means of vacuumsucking effect of a nozzle, and separating the component from the nozzleand mounting the same onto a predetermined mounting position of acircuit substrate by means of air blowing effect of the nozzle, whereinthe method including procedures for preventing occurrence of defectivesubstrates, which procedures comprising steps of; measuring air flowvolume blown from the nozzle at an air flow passage at a timingimmediately after completion of component mounting operation, which airflow passage is provided for supplying pressurized air to the nozzle;and making a judgment that the component has not been mounted onto thecircuit substrate, if the measurement value is smaller than apredetermined threshold.
 8. The method according to claim 7, wherein thethreshold comprising two thresholds, and said procedures comprisingsteps of: making a judgment that the component has not been mounted ontothe circuit substrate, if the measurement value is smaller than both ofthe thresholds; and making a judgment that the component has beenmounted onto the circuit substrate, but that a filter disposed at theair flow passage is clogged, if the measurement value is in between thetwo thresholds.
 9. The method according to claim 8, wherein saidprocedures comprising steps of: measuring blowing air flow volume at twodifferent timings immediately after completion of component mountingoperation; making a judgment whether or not the component has beenproperly mounted onto the circuit substrate based on the firstmeasurement value; and making a judgment either the component has beenmounted onto the circuit substrate but the filter is clogged, or thecomponent has not been mounted onto the circuit substrate based on thesecond measurement value.
 10. A method of component mounting for pickingup a component by means of vacuum sucking effect of a nozzle, andseparating the component from the nozzle and mounting the same onto apredetermined mounting position of a circuit substrate by means of airblowing effect of the nozzle, wherein the method including proceduresfor preventing occurrence of defective substrates, which procedurescomprising steps of; measuring differential of air flow volume blownfrom the nozzle at an air flow passage at a timing immediately aftercompletion of component mounting operation, which air flow passage isprovided for supplying pressurized air to the nozzle; and making ajudgment that the component has not been mounted onto the circuitsubstrate, if the differential of air flow volume decrease obtained bythe measurement is bigger than a predetermined threshold.
 11. The methodaccording to claim 10, wherein the threshold comprising two thresholds,and said procedures comprising steps of: making a judgment that thecomponent has not been mounted onto the circuit substrate, if thedifferential of air flow volume decrease obtained by the measurement isbigger than both of the thresholds; and making a judgment that thecomponent has been mounted onto the circuit substrate, but that a filterdisposed at the air flow passage is clogged, if the differential of airflow volume decrease obtained by the measurement is bigger than one ofthe thresholds but smaller than the other.
 12. The method according toclaim 11, wherein said procedures comprising steps of: measuringdifferential of air flow volume at two different timings immediatelyafter completion of component mounting operation; making a judgmentwhether or not the component has been properly mounted onto the circuitsubstrate based on the first measurement result; and making a judgmenteither the component has been mounted onto the circuit but the filter isclogged, or the component has not been mounted onto the circuitsubstrate based on the second measurement result.
 13. A method ofcomponent mounting for picking up a component by means of vacuum suckingeffect of a nozzle, and separating the component from the nozzle andmounting the same onto a predetermined mounting position of a circuitsubstrate by means of air blowing effect of the nozzle, wherein themethod including procedures for preventing occurrence of defectivesubstrates, which procedures comprising steps of; measuring blowing airpressure blown from the nozzle at an air flow passage at a timingimmediately after completion of component mounting operation, which airflow passage is provided for supplying pressurized air to the nozzle;and making a judgment that the component has not been mounted onto thecircuit substrate, if the measurement value is bigger than apredetermined threshold.
 14. The method according to claim 13, whereinthe threshold comprising two thresholds, and said procedures comprisingsteps of: making a judgment that the component has not been properlymounted onto the circuit substrate, if the measurement value is biggerthan both of the thresholds; and making a judgment that the componenthas been mounted onto the circuit substrate, but that a filter disposedat the air flow passage is clogged, if the measurement value is inbetween the two thresholds.
 15. The method according to claim 14,wherein said procedures comprising steps of: measuring blowing airpressure at two different timings immediately after completion ofcomponent mounting operation; making a judgment whether or not thecomponent has been properly mounted onto the circuit substrate based onthe first measurement value; and making a judgment either the componenthas been mounted onto the circuit substrate but the filter is clogged,or the component has not been mounted onto the circuit substrate basedon the second measurement value.
 16. A method of component mounting forpicking up a component by means of vacuum sucking effect of a nozzle,and separating the component from the nozzle and mounting the same ontoa predetermined mounting position of a circuit substrate by means of airblowing effect of the nozzle, wherein the method including proceduresfor preventing occurrence of defective substrates, which procedurescomprising steps of; measuring differential of blowing air pressureblown from the nozzle at an air flow passage at a timing immediatelyafter completion of component mounting operation, which air flow passageis provided for supplying pressurized air to the nozzle; and making ajudgment that the component has not been mounted onto the circuitsubstrate, if the differential of blowing air pressure decrease obtainedby the measurement is smaller than a predetermined threshold.
 17. Themethod according to claim 16, wherein the threshold comprising twothresholds, and said procedures comprising steps of: making a judgmentthat the component has not been mounted onto the circuit substrate, ifthe differential of blowing air pressure decrease obtained by themeasurement is smaller than both of the thresholds; and making ajudgment that the component has been mounted onto the circuit substrate,but that a filter disposed at the air flow passage is clogged, if thedifferential of blowing air pressure decrease obtained by themeasurement is smaller than one of the thresholds but bigger than theother.
 18. The method according to claim 17, wherein said procedurescomprising steps of: measuring differential of air flow volume at twodifferent timings immediately after completion of component mountingoperation; making a judgment whether or not the component has beenproperly mounted onto the circuit substrate based on the firstmeasurement result; and making a judgment either the component has beenmounted onto the circuit but the filter is clogged, or the component hasnot been mounted onto the circuit substrate based on the secondmeasurement result.
 19. A method of component mounting for picking up acomponent by means of vacuum sucking effect of a nozzle, and separatingthe component from the nozzle and mounting the same onto a predeterminedmounting position of a circuit substrate by means of air blowing effectof the nozzle, wherein the method including procedures for preventingoccurrence of defective substrates, which procedures comprising stepsof; measuring either one of blowing air flow volume, differential ofblowing air flow volume decrease, blowing air pressure, or differentialof blowing air pressure decrease of the air blown from the nozzle at anair flow passage at a timing immediately after completion of componentmounting operation, which air flow passage is provided for supplyingpressurized air to the nozzle; comparing the result of the measurementwith a predetermined corresponding threshold; making a judgment that thecomponent has been separated from the nozzle and mounted onto thecircuit substrate properly, if the blowing air flow volume or thedifferential of blowing air pressure decrease is bigger than thecorresponding predetermined threshold, or the differential of blowingair volume decrease or blowing air pressure is smaller than thecorresponding predetermined threshold, and then performing next roundcomponent pick up operation; making a judgment that the component hasnot been separated from the nozzle and that the circuit substrate ismissing the component, if the blowing air flow volume or thedifferential of blowing air pressure decrease is smaller than thecorresponding predetermined threshold, or the differential of blowingair volume decrease or blowing air pressure is bigger than thecorresponding predetermined threshold; stopping the component mountingapparatus; checking the nozzle, removing the component carried by thenozzle, and confirming that the nozzle is in a proper condition; andrestarting the component mounting apparatus for next round componentpick up operation.
 20. A method of component mounting for picking up acomponent by means of vacuum sucking effect of a nozzle, and separatingthe component from the nozzle and mounting the same onto a predeterminedmounting position of a circuit substrate by means of air blowing effectof the nozzle, wherein the method including procedures for preventingoccurrence of defective substrates, which procedures comprising stepsof; measuring either one of blowing air flow volume, differential ofblowing air flow volume decrease, blowing air pressure, or differentialof blowing air pressure decrease of the air blown from the nozzle at anair flow passage at a timing immediately after completion of componentmounting operation, which air flow passage is provided for supplyingpressurized air to the nozzle; comparing the result of the measurementwith a first predetermined corresponding threshold; making a judgmentthat the component has been separated from the nozzle and mounted ontothe circuit substrate properly, if the blowing air flow volume or thedifferential of blowing air pressure decrease is bigger than thecorresponding predetermined first thresholds, or the differential ofblowing air flow volume decrease or blowing air pressure is smaller thanthe corresponding predetermined first threshold, and then performingnext round component pick up operation; comparing the result of themeasurement with a second corresponding predetermined threshold, if theblowing air flow volume or the differential of blowing air pressuredecrease is smaller than the corresponding predetermined firstthreshold, or the differential of blowing air flow volume decrease orthe blowing air pressure is bigger than the corresponding predeterminedfirst threshold; making a judgment that the component has been mountedonto the circuit substrate but that a filter disposed at an air flowpassage is clogged, and generating an alarm, if the blowing air flowvolume or the differential of blowing air pressure decrease is biggerthan the corresponding predetermined second thresholds, or thedifferential of blowing air flow volume decrease or blowing air pressureis smaller than the corresponding predetermined second threshold; makinga judgment that the component has not been separated from the nozzle andthat the circuit substrate is missing the component, if the blowing airflow volume or the differential of blowing air pressure decrease issmaller than the corresponding predetermined second threshold, or thedifferential of blowing air volume decrease or the blowing air pressureis bigger than the corresponding predetermined second threshold;stopping the component mounting apparatus; checking the nozzle, removingthe component carried by the nozzle, and confirming that the nozzle isin a proper condition; and restarting the component mounting apparatusfor next round component pick up operation.
 21. The method according toclaim 20, wherein, after the step of generating an alarm, saidprocedures further comprising steps of: stopping the component mountingapparatus; checking the nozzle, removing the component carried by thenozzle, and confirming that the nozzle is in a proper condition; andrestarting the component mounting apparatus for next round componentpick up operation.
 22. The method according to claim 20, wherein theprocedures comprising step of: measuring either one of blowing air flowvolume, differential of blowing air flow volume decrease, blowing airpressure, or differential of blowing air pressure decrease of the airblown from the nozzle at an air flow passage at two different timingsimmediately after completion of component mounting operation, which airflow passage is provided for supplying pressurized air to the nozzle;comparing the result of the first measurement with the first threshold;and comparing the result of the second measurement with the secondthreshold.
 23. The method according to claim 19, wherein, between thestep of making a judgment that the circuit substrate is missing acomponent and the step of stopping the component mounting apparatus,said procedures further comprising steps of: discarding the componentcarried by the nozzle; skipping the component pick up and componentmounting operations at next round component mounting cycle; measuringeither one of blowing air flow volume, differential of blowing air flowvolume decrease, blowing air pressure, or differential of blowing airpressure decrease of the air blown from that particular nozzle at atiming immediately after air blowing operation; comparing the result ofthe measurement with the corresponding predetermined threshold or thefirst threshold; making a judgment that the component has been discardedproperly and performing next round component pick up operation withoutstopping the component mounting apparatus, if the blowing air flowvolume or the differential of blowing air pressure decrease is biggerthan the corresponding predetermined threshold or the first threshold,or the differential of blowing air flow volume decrease or blowing airpressure is smaller than the corresponding predetermined threshold orthe first threshold, and then performing next round component pick upoperation; making a judgment that the component has not been discardedproperly, if the blowing air flow volume or the differential of blowingair pressure decrease is smaller than the corresponding predeterminedthreshold or the first threshold, or the differential of blowing airflow volume decrease or blowing air pressure is bigger than thecorresponding predetermined threshold or the first threshold.
 24. Themethod according to claim 19, wherein after the step of making ajudgment that the circuit substrate is missing a component, saidprocedures further comprising a step of confirming whether or not thecomponent to be mounted on the circuit substrate is actually missingfrom the circuit substrate by checking that particular circuitsubstrate.
 25. The method according to claim 19, wherein when it isjudged that the circuit substrate is missing a component, the proceduresfurther includes steps of: picking up the missing component; andmounting the component onto that particular circuit substrate forrecovering the missing component.
 26. A component mounting apparatuscomprising: component supply for supplying component continuously; amounting head having nozzles for picking up components from thecomponent supply by means of air sucking effect, and separating andmounting the components onto predetermine respective mounting positionsof a circuit substrate by means of air blowing effect; a substrateholder for transporting and positioning the circuit substrate; an airsucking/blowing mechanism connected to the nozzles for providing airsucking effect and air blowing effect to the nozzle; and a controllerfor controlling overall operations of the component mounting apparatus,wherein the air sucking/blowing mechanism further comprising: either oneof a measuring meter capable of measuring blowing air flow volume ordifferential of the blowing air flow volume, or a pressure meter capableof measuring blowing air pressure or differential of the blowing airpressure, either one of which is disposed at an air flow passage forsupplying pressurized air to the nozzle, and for measuring eitherblowing air volume or pressure at a timing immediately after completionof blowing air; and a controller for comparing the measuring resultobtained by either one of the meters with a corresponding preliminaryinputted threshold, and for making a judgment whether or not thecomponent has been mounted properly.
 27. The component mountingapparatus according to claim 26, wherein the preliminary inputtedthreshold comprising two thresholds, and the controller being designedto make a judgment whether or not the component has been mountedproperly or not based on comparison between the measurement result andthe first threshold, and/or making judgment either the component hasbeen mounted onto the circuit substrate but the filter is clogged, orthe component has not been mounted onto the circuit substrate based oncomparison between the measurement result and the second threshold. 28.The component mounting apparatus according to claim 27, wherein themeasuring meter or the pressure meter measuring either one of blowingair flow volume, differential of blowing air flow volume decrease,blowing air pressure or differential of blowing air pressure decrease attwo different timings immediately after air blowing operation; and thecontroller making a judgment whether or not the component has beenproperly mounted onto the circuit substrate based on comparison betweenthe first measurement result and the corresponding first threshold, andmaking a judgment either the a filter disposed at air flow passage isclogged, or the component has not been mounted based on comparisonbetween the second measurement value and the corresponding secondthreshold.
 29. The component mounting apparatus according to claim 26,wherein the nozzle is structured to suck a component having a spanlength of equal to or less than 1.0 mm.